TITLE: GCN CIRCULAR NUMBER: 40386 SUBJECT: GRB 250427B : SVOM detection of a burst through offline search DATE: 25/05/07 16:58:28 GMT FROM: SVOM_group svomgroup@bao.ac.cn
M. Brunet (IRAP), N. Dagoneau (CEA), O. Godet (IRAP), S.J. Zheng (IHEP),
report on behalf of the SVOM team :
The SVOM/ECLAIRs telescope detected a transient source, labelled GRB 250427B, starting at 2025-04-27T20:57:56.9 UTC (Tb), through an offline search with the event-by-event data downloaded through the X-band ground station.
The burst was detected by several methods and within several energy ranges and timescales. The best detection is obtained by the image trigger with a signal-to-noise ratio of 7.8 within 8-120 keV over a time window of 10.24 seconds starting at Tb.
The lightcurve consists of a single pulse with a T90 of 11.0 +/-0.5 s in the 4-120 keV band.
The localization of the source is RA, Dec = 208.380, 54.716 degrees:
RA (J2000) = 13h53m31.2s Dec (J2000) = 54d42m57.6s
with a 90% C.L. radius of 11.6 arcmin (including systematic error of 6 arcmin added in quadrature).
We note that no bright X-ray source are found in the error box.
The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. ECLAIRs was developed jointly by APC, CEA, CNES, and IRAP.
The SVOM point of contact for this event is: Marius Brunet (IRAP) marius.brunet@irap.omp.eu. Please contact him by email if you require additional information regarding the SVOM follow-up of this burst.
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